' orTH£ w 



Vol. 2] Gardner. — Cytological Studies in Cyanophyceae. 243 



with albumin fixative if desired), after which t^e superflous 

 water is wiped off, and the remainder of the water allowed to 

 evaporate almost to dryness, when the plants are ready for fur- 

 ther treatment ; or one may place the material, free from debris, 

 in a large drop of water on the desired part of the slide, and 

 allow the water to evaporate. In this condition the plants usually 

 crawl out radially in a thin layer on the slide. 



If gelatinous forms are being used, a very small quantity of 

 clean material is placed on the slide and pressed gently with a 

 cover glass into a thin layer, after which the cover should be slid 

 off, not raised straight up. 



After staining, the material need not (except in very few 

 cases, e.g., some of the large thin-walled Oscillatorias) be run up 

 through the grades of alcohol, for shrinkage will not occur to any 

 detrimental degree if 90 per cent., and then absolute alcohol be 

 dropped on directly with a wash-bottle. For preliminary exami- 

 nation clove oil is best, for this clears the plants and takes out the 

 water, and, if permanent mounts are desired, they can be trans- 

 ferred directly to balsam. Clove oil cannot always be used be- 

 cause some of the stains {e.g., most of the violets) are so readily 

 soluble in it. I have found, however, that in general the violets 

 are not very useful, and, having found better stains, have almost 

 abandoned their use. 



End views of cells of the large species of Oscillatorias and 

 some other genera are very desirable for getting at the structure 

 of the nucleus. For this purpose a method has been worked out 

 which is vastly superior to the embedding and sectioning method. 

 This method consists in using a killing agent which will affect the 

 cross-cell walls in such a way as to cause the cells to separate 

 easily. In selecting such an agent it was necessary that one be 

 found which would not cause the trichomes to shrink, and also 

 one which could be followed by a variety of good differential 

 stains. 



Alcohol will serve this purpose in some of the thin-walled 

 short-celled forms, but the cells do not separate so readily as is 

 desirable, and a large number of them become broken and dis- 

 torted. The material is killed in 95 per cent, alcohol for half an 

 hour, after which the slides with the mounted plants are placed 



